Rationale: Edema fluid resorption is critical for gas exchange and requires active epithelial ion transport by Na,K-ATPase and other ion transport proteins. Objectives: In this study, we sought to determine if alveolar fluid clearance (AFC) is stimulated by 3,3′,5 triiodo-L-thyronine (T 3). Methods: AFC was measured in in situ ventilated lungs and ex vivo isolated lungs by instilling isosmolar 5% bovine serum albumin solution with fluorescein-labeled albumin tracer and measuring the change in fluorescein isothiocyanate-albumin concentration over time. Measurements and Main Results: Systemic treatment with intraperitoneal injections of T3 for 3 consecutive days increased AFC by 52.7% compared with phosphate-buffered saline-injected control rats. Membranes prepared from alveolar epithelial cells from T3-treated rats had higher Na,K-ATPase hydrolytic activity. T3 (10-6M), but not reverse T3 (3,3′,5′ triiodo-L-thyronine), applied to the alveolar space increased AFC by 31.8% within 1.5 hours. A 61.5% increase in AFC also occurred by airspace instillation of T3 in ex vivo isolated lungs, suggesting a direct effect of T3 on the alveolar epithelium. Exposure of rats to an oxygen concentration of greater than 95% for 60 hours increased wet-to-dry lung weights and decreased AFC, whereas the expression of thyroid receptor was not markedly changed. Airspace T3 rapidly restored the AFC in rat lungs with hyperoxia-induced lung injury. Conclusions: Airspace T3 rapidly stimulates AFC by direct effects on the alveolar epithelium in rat lungs with and without lung injury.
|Original language||English (US)|
|Number of pages||7|
|Journal||American journal of respiratory and critical care medicine|
|State||Published - Sep 1 2008|
Copyright 2008 Elsevier B.V., All rights reserved.
- Acute respiratory distress syndrome
- Alveolar Na,K-ATPase
- Alveolar fluid clearance
- Thyroid hormone
- Type 2 cell